Increasingly stringent statutory regulations in relation to permissible pollutant emissions of motor vehicles in which internal combustion engines are disposed make it necessary to keep said pollutant emissions to an absolute minimum during the operation of the internal combustion engine. This can be realized on the one hand by reducing the pollutant emissions that are produced during the combustion of the air/fuel mixture in the respective cylinder of the internal combustion engine. On the other hand exhaust gas aftertreatment systems are used in internal combustion engines, said exhaust gas aftertreatment systems converting the pollutant emissions generated during the combustion process of the air/fuel mixture in the respective cylinders into innocuous substances. For this purpose catalytic converters are used which convert the carbon monoxide, hydrocarbons and nitrogen oxides into innocuous substances. Both the targeted influencing of the generation of the pollutant emissions during combustion and the converting of the pollutant components with a high degree of efficiency by means of an exhaust gas catalytic converter require a very precisely adjusted air/fuel ratio in the respective cylinder.
In this connection it must be ensured that the components of the exhaust gas aftertreatment system also operate in the desired manner over a long service life and that faults are reliably detected.
In this connection it is also important that faults in sensors, such as, for example, exhaust gas probes, are accurately and reliably detected.